This invention relates generally to an optical scanning device for effecting two-dimensional scanning of laser beams and an image forming device as well, and more particularly, to a device for forming an optically inputted two-dimensional image and a recording method thereof.
A conventional image forming device is disclosed in Japanese Patent Laid-Open No. 216126/1984 as a device using thermoplastic material as a medium to be modulated. In addition, SID 87 DIGEST p. 367 (1987) and SID 85 DIGEST P. 260 (1985), disclose devices wherein an image stored on a light valve employing a smectic A (hereinafter SmA) liquid crystal is recorded on sensitizing paper or a photosensitive material.
Another prior art device is disclosed in vol. 27, No. 1, p. 20 (1975) of the NHK Technical Institute. This device is a two-dimensional scanning device which requires a multiplicity of highly accurate anamorphic lenses in order to make quick corrections with respect to horizontal deflection and vertical deflection. These corrections are made to correct curvatures of the field and of the image surface inclination of a polygon-mirror. The two-dimensional scanning device, which employs vector scan, is based on a galvano-mirror which requires a special focal point correcting means for correcting the curvature of the field.
A great majority of conventional optical image storing devices utilize thermooptic effects in which the storage of an input image can not be controlled electronically. This presents a problem in that a substantial amount of time is required to form the image. A second problem associated with the prior art devices is that driving can cause deterioration of the electrooptic medium. An additional problem is that there is no simple and highly accurate means for inputting the image.
Generally speaking in accordance with the present invention, an image forming and two-dimensional optical scanning device is provided.
The optical image storing device and the two-dimensional optical scanning device according to the present invention have the following characteristics.
The light valve (hereinafter PALV) includes an electrooptic medium which makes a state-transition by photoelectric converting action of the photoconductive material.
The electrooptic effect PALV forms the image by use of an electrooptic medium which exhibits a bi-stability. The state of the medium is dependent on a threshold voltage and on a threshold intensity of the input beam.
The electrooptic effect PALV employs a dielectric liquid crystal as the electrooptic medium which exhibits the bi-stability and an oblique vapor deposition film composed of an inorganic oxide formed on a surface contiguous to the liquid crystal of at least one of a pair of substrates which sandwich the liquid crystal.
The electrooptic effect PALV is constructed essentially of a photoconductive material, a read-out beam separating means, an electrooptic medium and an electrode.
The image reading means is an image output optical system which irradiates the photosensitive medium with the PALV image. The PALV image beams have a plurality of different wavelengths or wavelength regions. The spectrum of the image output optical system is different from the spectrum of the write beam of the image inputting means.
The image inputting means of the two-dimensional optical scanning device projectively inputs a two-dimensional optical image in synchronization with the recording electric field applying means. It can projectively input a plurality of two-dimensional optical images in synchronization with one of the positive and negative cycles of the recording electric field applying means. The plurality of two-dimensional optical images can be input time sequentially in synchronization with the recording electric field applying means 0.
The two-dimensional optical scanning device includes light beam generating means, a horizontal deflector for effecting horizontal scanning of light beams, a focusing optical means for spotting the light beams on the scanned plane to form an image and an orthogonal deflection for deflecting the light beams deflected by the horizontal deflector in orthogonal directions.
The two-dimensional scanning device is composed of a rotating polygon-mirror deflector for effecting deflective scanning of light beams from the light beam generating means, a focusing optical system for spotting the light beams on the scanned plane to form an image and a linearly movable mirror. The mirror is linearly movable within a specified plane, for reflecting a traveling direction of the light beams deflected by the rotating polygon-mirror deflector at a given angle. In this device, a scanning length 1p, a displacement of the linear movable mirror 1s, an angle (=xcex1/2) made by the linearly movable mirror and the specified plane and an angle xcex2 made by the scanned plane and the specified plane satisfy the following two formulae:
1p/sinxcex1=1s/sinxcex2
xcex1+2xcex2=xcfx80
The scanning system synchronizes with a reference signal transmitted from a detecting unit for a horizontal scanning cycle of the horizontal deflector.
In the two-dimensional optical scanning device, a scanning system synchronizes with a reference signal defined as a horizontal synchronous signal transmitted from an image signal source. In addition, the scanning system and the driving signal of the recording electric field applying means synchronize with the reference signal which can be transmitted from a detecting unit for a horizontal scanning cycle of the horizontal deflector or from the image signal source.
A driving signal of the recording electric field applying means of the PALV is an AC signal consisting of an erasing signal, a write driving signal synchronized with an image input and a hold period with a duration of one frame.
The write driving signal has a cycle of one polarity corresponding to the writing process, the cycle synchronizing with an image beam input from the image inputting means. When the write driving signal possesses positive polarity, it synchronizes with a positive image input. When the write driving signal possesses negative polarity, it synchronizes with a negative image input.
The erasing signal assumes a polarity opposite to a polarity corresponding to writing of the write signal during an irradiation of the erasing beam. In addition, the erasing signal has an amplitude sufficient to permit an electrooptic medium to effect a state transition during non-irradiation of the beam.
The electric field applying means is in a high impedance or released state during the hold period. The electrooptic medium transits to or is held in any one of the states selected just prior to the hold period.
The beam intensity of the image inputting means consists of a first intensity level at which the PALV can be transited to a different state with a sole input beam intensity and a second intensity level at which the PALV can not be transited with the sole input beam intensity but can be transited to a different state with an intensity of a sum of a plurality of input beams.
Similarly, the driving signal of the recording electric field applying means of the PALV consists of a first voltage level at which the PALV can be transited to a different state with a sole input beam intensity and a second voltage level at which the PALV can not be transited to a different state with the sole input beam intensity but can be transited with an intensity of a sum of a plurality of input beams.
The image read-out means is an image inputting means to a photosensitive material or in another embodiment, the image read-out means is an image output optical system output to a screen. The image read-out means outputs the same image or a mirror image to the photosensitive medium or screen.
A two-dimensional optical scanning device can include: a light beam generating means a rotating polygon-mirror deflector for effecting deflective scanning of the light beams, a focusing optical means for spotting the light beams on the scanned plane to form an image and a linearly movable mirror which is linearly movable within a specified plane for reflecting a traveling direction of the light beams deflected by the rotating polygon-mirror deflector at a given angle, wherein a scanning length 1p, a moving quantity 1s of the linear movable mirror, an angle (=xcex1/2) made by the linear movable mirror and the specified plane and an angle xcex2 made by the scanned plane and the specified plane satisfy the following two formulae:
1p/sinxcex1=1s/sinxcex2
xcex1+2xcex2=xcfx80
The focusing optical system includes an optical system for correcting a degree of parallelism of a rotary axis with each mirror of the polygon-mirror.
Accordingly, it is an object of the present invention to provide an improved image forming and optical scanning device.
Another object of the present invention is to provide an image forming and optical scanning device which irradiates the photoconductive material with an input beam by providing a novel driving method and forms a highly accurate image at a high speed.
A further object of the present invention is to provide the more sophisticated functions of a display and a printer for storing and displaying the scanned images.
A still further object of the present invention is to provide both a two-dimensional optical scanning device for simple and high quality raster scanning and an image forming device using this two-dimensional optical scanning device.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combination(s) of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.